Question

The value of ΔH°rxn for the reaction below is –1036 kJ:

2H2​S(g)+3O2​(g) -> 2SO2​(g)+2H2​O(g)

Estimate the average energy of the individual bonds in SO2 from the appropriate average bond energies. (in kJ/mol)

Answer 1

The average energy of the individual bonds in SO2 can be determined using the bond energies of the other bonds present in the reaction . These are :

H-S = 347 KJ

O-O = 142 KJ

O=O = 495 KJ

H-O = 463 KJ

The bond energies of the reactants are subtracted from the total bond energies of the products to give the enthalpy of the reaction.

Let the bond energy of SO2 bonds be X , so putting all the values we get :

-1036 = (4 x 347 + 3 x 495) - ( 4xX + 4x463)

X = 514.25 KJ/mol

So the average bond energy of the individual bonds in SO2 is 514.25 KJ.